Hidden properties are not shown for registered users
A property can be hidden then it will be not shown in the API output for not registered visitors. Registered users will instead get back the hidden properties from the API. There seems to be another check implemented in the frontend, because I'm not able to see the hidden properties in the detail page when I'm logged in. I'm not 100% sure but I think it makes sense to show the hidden properties to the registered users (it is mostly curational information like that the accessibleAt produces a 404).